Search tips
Search criteria

Results 1-5 (5)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Lack of the presynaptic RhoGAP protein oligophrenin1 leads to cognitive disabilities through dysregulation of the cAMP/PKA signalling pathway 
Loss-of-function mutations in the gene encoding for the RhoGAP protein of oligophrenin-1 (OPHN1) lead to cognitive disabilities (CDs) in humans, yet the underlying mechanisms are not known. Here, we show that in mice constitutive lack of Ophn1 is associated with dysregulation of the cyclic adenosine monophosphate/phosphate kinase A (cAMP/PKA) signalling pathway in a brain-area-specific manner. Consistent with a key role of cAMP/PKA signalling in regulating presynaptic function and plasticity, we found that PKA-dependent presynaptic plasticity was completely abolished in affected brain regions, including hippocampus and amygdala. At the behavioural level, lack of OPHN1 resulted in hippocampus- and amygdala-related learning disabilities which could be fully rescued by the ROCK/PKA kinase inhibitor fasudil. Together, our data identify OPHN1 as a key regulator of presynaptic function and suggest that, in addition to reported postsynaptic deficits, loss of presynaptic plasticity contributes to the pathophysiology of CDs.
PMCID: PMC3843891  PMID: 24298161
amygdala; presynaptic plasticity; adenylate cyclase; PKA; fasudil
2.  Coronin 1 Regulates Cognition and Behavior through Modulation of cAMP/Protein Kinase A Signaling 
PLoS Biology  2014;12(3):e1001820.
The evolutionarily conserved protein coronin 1 is needed for activating the cyclic AMP signaling pathway in the brain and is important for cognition and behavior.
Cognitive and behavioral disorders are thought to be a result of neuronal dysfunction, but the underlying molecular defects remain largely unknown. An important signaling pathway involved in the regulation of neuronal function is the cyclic AMP/Protein kinase A pathway. We here show an essential role for coronin 1, which is encoded in a genomic region associated with neurobehavioral dysfunction, in the modulation of cyclic AMP/PKA signaling. We found that coronin 1 is specifically expressed in excitatory but not inhibitory neurons and that coronin 1 deficiency results in loss of excitatory synapses and severe neurobehavioral disabilities, including reduced anxiety, social deficits, increased aggression, and learning defects. Electrophysiological analysis of excitatory synaptic transmission in amygdala revealed that coronin 1 was essential for cyclic–AMP–protein kinase A–dependent presynaptic plasticity. We further show that upon cell surface stimulation, coronin 1 interacted with the G protein subtype Gαs to stimulate the cAMP/PKA pathway. The absence of coronin 1 or expression of coronin 1 mutants unable to interact with Gαs resulted in a marked reduction in cAMP signaling. Strikingly, synaptic plasticity and behavioral defects of coronin 1–deficient mice were restored by in vivo infusion of a membrane-permeable cAMP analogue. Together these results identify coronin 1 as being important for cognition and behavior through its activity in promoting cAMP/PKA-dependent synaptic plasticity and may open novel avenues for the dissection of signal transduction pathways involved in neurobehavioral processes.
Author Summary
Memory and behavior depend on the proper transduction of signals in the brain, but the underlying molecular mechanisms remain largely unknown. Coronin 1 is a member of a highly conserved family of proteins, and although its gene lies in a chromosome region associated with neurobehavioral dysfunction in mice and men, it has never been directly ascribed a specific function in the brain. Here we show that coronin 1 plays an important role in cognition and behavior by regulating the cyclic AMP (cAMP) signaling pathway. We find that when cell surface receptors are activated, coronin 1 stimulates cAMP production and activation of protein kinase A. Coronin 1 deficiency resulted in severe functional defects at excitatory synapses. Furthermore, in both mice and humans, deletion or mutation of coronin 1 causes severe neurobehavioral defects, including social deficits, increased aggression, and learning disabilities. Strikingly, treatment with a membrane-permeable analogue of cAMP restored synaptic plasticity and behavioral defects in mice lacking coronin 1. Together this work not only shows a critical role for coronin 1 in neurobehavior but also defines a role for the coronin family in regulating the transmission of signals within cells.
PMCID: PMC3965382  PMID: 24667537
3.  Forebrain Deletion of αGDI in Adult Mice Worsens the Pre-Synaptic Deficit at Cortico-Lateral Amygdala Synaptic Connections 
PLoS ONE  2012;7(1):e29763.
The GDI1 gene encodes αGDI, which retrieves inactive GDP-bound RAB from membranes to form a cytosolic pool awaiting vesicular release. Mutations in GDI1 are responsible for X-linked Intellectual Disability. Characterization of the Gdi1-null mice has revealed alterations in the total number and distribution of hippocampal and cortical synaptic vesicles, hippocampal short-term synaptic plasticity and specific short-term memory deficits in adult mice, which are possibly caused by alterations of different synaptic vesicle recycling pathways controlled by several RAB GTPases. However, interpretation of these studies is complicated by the complete ablation of Gdi1 in all cells in the brain throughout development. In this study, we generated conditionally gene-targeted mice in which the knockout of Gdi1 is restricted to the forebrain, hippocampus, cortex and amygdala and occurs only during postnatal development. Adult mutant mice reproduce the short-term memory deficit previously reported in Gdi1-null mice. Surprisingly, the delayed ablation of Gdi1 worsens the pre-synaptic phenotype at cortico-amygdala synaptic connections compared to Gdi1-null mice. These results suggest a pivotal role of αGDI via specific RAB GTPases acting specifically in forebrain regions at the pre-synaptic sites involved in memory formation.
PMCID: PMC3264564  PMID: 22291894
4.  Pre and Post Synaptic NMDA Effects Targeting Purkinje Cells in the Mouse Cerebellar Cortex 
PLoS ONE  2012;7(1):e30180.
N-methyl-D-aspartate (NMDA) receptors are associated with many forms of synaptic plasticity. Their expression level and subunit composition undergo developmental changes in several brain regions. In the mouse cerebellum, beside a developmental switch between NR2B and NR2A/C subunits in granule cells, functional postsynaptic NMDA receptors are seen in Purkinje cells of neonate and adult but not juvenile rat and mice. A presynaptic effect of NMDA on GABA release by cerebellar interneurons was identified recently. Nevertheless whereas NMDA receptor subunits are detected on parallel fiber terminals, a presynaptic effect of NMDA on spontaneous release of glutamate has not been demonstrated. Using mouse cerebellar cultures and patch-clamp recordings we show that NMDA facilitates glutamate release onto Purkinje cells in young cultures via a presynaptic mechanism, whereas NMDA activates extrasynaptic receptors in Purkinje cells recorded in old cultures. The presynaptic effect of NMDA on glutamate release is also observed in Purkinje cells recorded in acute slices prepared from juvenile but not from adult mice and requires a specific protocol of NMDA application.
PMCID: PMC3261884  PMID: 22276158
5.  Synaptic Maturation at Cortical Projections to the Lateral Amygdala in a Mouse Model of Rett Syndrome 
PLoS ONE  2010;5(7):e11399.
Rett syndrome (RTT) is a neuro-developmental disorder caused by loss of function of Mecp2 - methyl-CpG-binding protein 2 - an epigenetic factor controlling DNA transcription. In mice, removal of Mecp2 in the forebrain recapitulates most of behavioral deficits found in global Mecp2 deficient mice, including amygdala-related hyper-anxiety and lack of social interaction, pointing a role of Mecp2 in emotional learning. Yet very little is known about the establishment and maintenance of synaptic function in the adult amygdala and the role of Mecp2 in these processes. Here, we performed a longitudinal examination of synaptic properties at excitatory projections to principal cells of the lateral nucleus of the amygdala (LA) in Mecp2 mutant mice and their wild-type littermates. We first show that during animal life, Cortico-LA projections switch from a tonic to a phasic mode, whereas Thalamo-LA synapses are phasic at all ages. In parallel, we observed a specific elimination of Cortico-LA synapses and a decrease in their ability of generating presynaptic long term potentiation. In absence of Mecp2, both synaptic maturation and synaptic elimination were exaggerated albeit still specific to cortical projections. Surprisingly, associative LTP was unaffected at Mecp2 deficient synapses suggesting that synaptic maintenance rather than activity-dependent synaptic learning may be causal in RTT physiopathology. Finally, because the timing of synaptic evolution was preserved, we propose that some of the developmental effects of Mecp2 may be exerted within an endogenous program and restricted to synapses which maturate during animal life.
PMCID: PMC2896423  PMID: 20625482

Results 1-5 (5)